A wide variety of equipment for applying liquids such as paint, varnish, or other coating materials are known. Some types of hand held applicator devices for applying liquid coating materials to a surface have a supply vessel attached directly to the applicator device that utilize the force of gravity to supply the coating material to the applicator device.
One example of an applicator device that utilizes a gravity-feed supply vessel is a hand-held spray assembly 10 for applying coating materials such as paint as shown in FIG. 1. As shown in FIG. 1, the spray assembly 10 includes a spray gun 12 coupled to a supply vessel 14. The spray gun 12 is also coupled to a pressure source 16, such as an air compressor or gas bottle. The spray gun 12 includes a nozzle 18 for applying a spray or stream 20 of a liquid coating material (e.g. paint) onto a workpiece 22, and a trigger 24 for controlling a rate of flow of the liquid coating material from the nozzle 18 in a conventional manner widely known in the art.
The supply vessel 14 includes a threaded aperture 26 that threadedly engages a threaded mounting nipple 28 on the spray gun 12, and a removable cover 34 that allows the supply vessel 14 to be filled. The supply vessel 14 is rigidly attached onto the threaded mounting nipple 28 of the spray gun 12 in a tilted position such that a central axis 30 of the supply vessel 14 forms a tilt angle I with respect to a nozzle axis 32 passing through a centerline of the nozzle 18. Typically, the tilt angle I of the conventional spray assembly 10 is approximately 45 degrees, allowing gravitational feed of the liquid coating material from the supply vessel 14 into the spray gun 12 throughout a range of positions of the nozzle axis 32, including vertical (as shown in FIG. 1) to horizontal and slightly beyond.
Although desirable results have been achieved using prior art spray assemblies 10, some operational drawbacks exist. For example, in an operating position 36 shown in FIG. 1, the nozzle axis 32 is positioned perpendicular to the horizontal surface of the workpiece 22 so that the spray 20 is applied uniformly to the workpiece 22. In this position 36, however, the liquid coating material in the supply vessel 14 may only be filled to a maximum safe-operating level 38. Thus, the interior volume of the supply vessel 14 is typically not fully utilized when the spray assembly 10 is operated in the operating position 36. If the spray assembly 10 is rotated in a clockwise direction R so that the nozzle axis 32 is not perpendicular to the workpiece 22, the supply vessel 14 may be filled to a higher level, however, in such a rotated position (not shown) the spray 20 is not uniformly applied to the workpiece 22, resulting in an unacceptable degradation of performance. Also, when the nozzle axis 32 is rotated away from the perpendicular position 36 the transfer efficiency defined as that percentage of the spray 20 that actually adheres to the surface of the workpiece 22 is reduced, resulting in increased waste and possibly adverse conditions within the surrounding atmosphere. For these reasons, the interior volume of the supply vessel 14 is typically not fully utilized, and the supply vessel 14 must be filled more frequently during operation of the spray assembly 10, resulting in decreased efficiencies and higher costs.
Similarly, FIG. 2 shows the spray assembly 10 in an upwardly directed position 40. In this position, the liquid coating material in the supply vessel 14 flows to a non-operational level 42 so that no coating material is supplied to the spray gun 12. Consequently, the spray gun 12 only emits a spray of gas 44 from the pressure source 16. Furthermore, in the upwardly directed position 40, the coating material exerts pressure on the removable cover 34, and the danger of an accidental spill 46 of the coating material is increased.